This disclosure generally relates to implantable devices for controlled drug delivery without a pre-defined orifice.
Many current drug delivery devices rely on at least one orifice to permit the release of drugs from the devices. While an orifice may allow for some control over drug release, orifice-containing devices may potentially expel an undesirable amount of drug when compressed after deployment. For example, an orifice-containing device deployed in the bladder may be compressed during bladder contraction, thereby forcing an undesirable amount of drug out of the orifice. The compression of orifice-containing devices may release toxic amounts of drugs, especially when the drugs are potent, such as anti-cancer drugs.
This problem can be mitigated, to some degree, by decreasing the size of the orifice of a particular device. As the size of the orifice decreases, however, the likelihood that the orifice will clog after deployment increases. A clogged orifice is undesirable because it often leads to less reproducible drug release, or it may prevent drug release entirely.
Aside from possible mechanical difficulties, adding an orifice to a device increases the device's complexity and cost of the components and/or manufacturing. This is especially true when an orifice of a small and precise diameter, such as one ranging from 75 to 300 microns, is needed to ensure that the device is capable of releasing drug at a desired rate.
In other cases, a drug delivery device may not have a release orifice and release of drug is controlled by diffusion from a matrix material and/or through a wall. Such configurations which rely on diffusion, however, may limit the drug release kinetics that can be achieved and/or may limit the range of suitable materials of construction to ones that lack the desired biocompatibility, stability, sterilizability, and mechanical properties, including manufacturability, wall thickness, flexibility, etc.
There exists a need for a drug delivery device that overcomes one or more of these disadvantages.